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Yield-boosting microbes

Researchers are studying Dean Glenney’s fencerow farming system (shown here at 30 days after planting), which involves strip cropping, no-till and controlled traffic practices.     Photo by A&L Biologicals.

Farmers often ask the question, “Why is my neighbour getting double my yields, even though we both use the same cultivar and the same fertility package?”

According to George Lazarovits, research director at A&L Biologicals, the answer could lie in the types of microbes in their fields. So the company, a research facility with a focus on healthy agricultural ecosystems, is working on a project with some Ontario growers to investigate this possibility.

Understanding microbial communities in soil and plants is no simple task. These communities can have a wide diversity of species and huge numbers of organisms. The recent and remarkable advances in DNA sequencing technology, and the rapid drop in sequencing costs, are allowing researchers to sequence the genetic material from these microbial communities, generating enormous amounts of data. Then the researchers have to sort through all of that data to try to figure out which components are most important for high yielding crops.

“A very large percentage of organisms in the soil and on roots have never been identified or sequenced,” Lazarovits notes. “[So if we do very detailed DNA sequencing of the samples, we can’t relate most of the genetic data to specific organisms.] And – more importantly – we don’t know what the unknown organisms do. Are they fixing nitrogen? Are they producing antibiotics that act as plant protectants? Are they giving plants hormone stimulants that make them grow faster? Are they involved directly in the plant’s ability to synthesize chemicals?”

So how can the researchers go about identifying which microbes are key to healthy, productive crops? “First you have to identify where and when to look – you have to find the haystack that has the needle in it. Once you find the right haystack, then you can start searching for the needle,” Lazarovits explains.
He thinks Dean Glenney’s farm in the Dunnville area of southwestern Ontario is one of those “haystacks.” Earlier this year, the Ontario Soil and Crop Improvement Association (OSCIA) named Glenney as its 2015 Soil Champion.

Lazarovits met Glenney at a conference in Montreal where Lazarovits was speaking about microbes in crop production and Glenney was speaking about his novel farming system that produces corn yields of around 300 bushels per acre in a region where the average is about half that.

Glenney asked Lazarovits why his farming system produces such high corn yields. “I said, ‘I haven’t a clue, but it would sure be a great model system to study,’” Lazarovits says. “So, through this project, we’ve been trying to unravel what is going on.”

Glenney developed his unique system because he noticed corn planted near fencerows was higher yielding than elsewhere in the field. So he gradually changed from a conventional production system to a system that tries to recreate the yield-boosting conditions along his fencerows.

His system, which he calls “fencerow farming,” includes such practices as no-till, controlled traffic and strip cropping. He has a corn-soybean rotation and grows the two crops in alternating strips; each strip is four metres wide and 80 metres long. He seeds into exactly the same rows every year.

Glenney has been using this system for about 15 years. “According to Dean, for the first five years he didn’t get any yield increases with this system,” Lazarovits says. “But in the sixth year, he started to see some increases, and he continued to see yield increases for a 10-year period after that.”

The project is led by Rafiq Islam, a research scientist at A&L Biologicals. One of the project’s main objectives is to determine if the microbial ecosystem in Glenney’s fields is enhancing the performance of his corn crops. As part of that, the researchers hope to figure out how best to assess a crop field’s microbial ecosystem. They would also like to identify practices that would help Glenney’s farm and other farms to become more productive.

Initial study
The project started in 2012 with a two-year study to identify key biological and non-biological factors contributing to Glenney’s higher corn yields. The study compared conditions at Glenney’s farm and a neighbour’s farm, with one site on each farm in each year of the study, and four randomly selected replicate plots at each site. 

The neighbour’s production system differs from Glenney’s in a number of ways. For example, the neighbour has a corn-corn-soybean rotation, he tills the soil before planting, and he doesn’t use strip cropping or controlled traffic practices.

For the study, both Glenney and his neighbour planted the same corn hybrid and used their normal production practices.

The researchers measured a wide range of factors, including soil characteristics, plant populations, nutrient levels in the soil and the plants, plant height and biomass, leaf chlorophyll content, and root and ear disease levels. They also examined the microbial communities on and in the roots, and inside the stems and leaves. As well, they determined grain yields, grain nutritional values, production costs and net returns.

To assess the microbial communities, the researchers used a molecular biology technique that identifies a small percentage of the most common microbes. This allows them to compare how similar or different the communities are.

Highlights of findings
The corn crops on Glenney’s sites had 75 per cent higher yields and were four times more profitable than the corn crops on the neighbour’s sites.

The researchers determined that 21 per cent of the higher yields was due to Glenney’s somewhat earlier seeding dates and higher seeding rates, and to the lower incidence and severity of ear disease. The researchers think the lower ear disease levels may be due to beneficial effects from the distinctive microbial community at the Glenney sites.

Although both farms had high levels of microbial activity, the microbiological communities were “different as day and night between the two farms,” Lazarovits notes. “The largest group of organisms present in Dean’s field are a group of bacteria called the fluorescent Pseudomonas. (They glow white under ultraviolet light, which is why they are called fluorescent.) These bacteria are known to be suppressive to diseases; they produce a whole slew of antibiotics. So it is quite possible these bacteria are acting as internal fungicides that protect the plants from diseases.”

The other 54 per cent of Glenney’s higher yields resulted from more productive ears. The ears were longer and wider and had more kernels per cob, the kernel weights were higher, and the grain weights per plant were much higher. The researchers think the beneficial effects of the microbial community might be contributing this higher productivity.

The sites on both farms had sandy soils; the neighbour’s soil had more organic matter. Although the researchers found various differences in soil nutrient levels between the sites, plant tissue analyses indicated the plants likely didn’t have prolonged nutrient deficiencies. So the researchers think soil fertility was probably not a major cause of the yield differences.

The researchers found the corn root systems at the Glenney sites became larger, longer, thicker and more branched. This implies the roots could move more easily through Glenney’s soil, likely because it was less compacted than the neighbour’s soil. Better root systems enhance nutrient and water uptake, which could have contributed to the higher yields.

Root disease levels varied considerably, but overall they were slightly higher at the Glenney sites, suggesting those sites had higher levels of soil-borne pathogens.

Next phase
In the current phase of the project, the researchers are conducting several studies to better understand how to work with microbial systems to enhance crop yields.

“According to the literature, the theoretical yield for corn in southwestern Ontario should be around 425 bushels. Can we push Dean’s yields from 300 to 400 bushels by changing some things in his system?” Lazarovits asks. “We also want to see if we can speed up the technology on other farm sites. If [the yield boost] is microbiological, could you transfer those microbes to other sites by some other technology, rather than by repeating what Dean has done, so instead of taking six years, it might take three years?”
In a study that started in 2014, the researchers are examining the effects of two changes to Glenney’s system on crop yields and the microbial community.

One change is tillage. Each year before planting, Glenney is tilling one side of each of the two strips that he has allocated to the project.

“One possibility is if you don’t disturb an ecosystem for a very long time, you build up a community in the soil that becomes associated with corn. So the bacteria are there to colonize the plants very rapidly,” Lazarovits says. “However, if you plow the soil, then you spread the bacteria all over the place. So you get a lot more bacteria of different types colonizing the plant, but they never reach a critical mass to benefit the plant.”

The other change is to add a green manure crop into the rotation. Last year, the research team grew plots of mustard, winter pea, and a plant that is related to corn, and plowed those crops into the soil as green manures. In 2015, those plots will be planted back to soybeans and corn.

Lazarovits explains that, with just a two-crop rotation, certain detrimental organisms might build up, which could be why Glenney’s corn yields have levelled off. The researchers want to see if green manuring might hamper some of the detrimental organisms, while maintaining the beneficial ones.

In another study, which will start this year, the researchers will be looking at microbial communities in other farmers’ fields. “Every farmer has zones in their fields with very high yields and zones with very poor yields. We want to see if the microbiology is correlated with the yields,” Lazarovits says.

Another aspect the researchers are planning to explore is why Glenney’s agro-ecosystem doesn’t provide the same sort of yield benefits to his soybean crops. “While Dean gets reasonably good soybean yields, he has not had the increasing yields that he has seen with corn,” Lazarovits notes.

In addition, the researchers are now collaborating with Greg Gloor, a medical microbiologist at the University of Western Ontario, who is using advanced techniques to sequence microbes for the project.
Lazarovits is excited about what could be learned by understanding the links between microbial communities and crop yields. “We think this is really going to be the next phase of agriculture. We are going to be able to understand how to grow crops in ways that take advantage of nature.”

June 1, 2015  By Carolyn King